Paul McIntyre, Materials Science & Engineering, Stanford University
This exploratory program aims at investigating a novel multijunction solar cell design to address the high fabrication costs of traditional multijunction devices, which use expensive-to-grow, high-quality semiconductor single crystals. The proposed design uses vertical semiconductor nanowire arrays grown on inexpensive polycrystalline germanium substrates, and takes advantage of the elastic dilatation property of nanowires that can relax misfit trains and allows the growth of high-quality nanowire heterojunctions with no dislocations. The program focuses on three enabling methods required for nanowire multijunction solar cells: 1) catalysis of Ge nanowire growth using inexpensive metal catalysts which, unlike the standard Au catalyst, do not produce deep carrier traps in the Ge bandgap; 2) nucleation and growth of dense, vertical Ge nanowire arrays on (111)-oriented polycrystalline Ge thin films on inexpensive glass substrates; and 3) formation of heterostructure GaAs/Ge nanowires by continuous, locally catalyzed deposition on Ge wires using Ga and As precursors.
- Hu, S., A.F. Marshall, and P.C. McIntyre. “Interface-controlled low-temperature metal-induced crystallization of germanium films on amorphous substrates.” Adv. Mater. (submitted, 2010).